Seedbeds for agriculture and foundations for construction sites are typically prepared by forcing strong metal shanks or tines through the compacted soil. The shanks are mounted to a cultivator frame that is pulled by a tractor through a drawbar or mounted to a tool bar that is attached to a tractor by means of a three point hitch.
It has been common for the attachment of the shanks to the frames to be such that the shanks can be shifted laterally to permit mounting at different lateral spacings between shanks. It has also been common for the shanks to be releasably mounted to prevent damage to the shanks, frame, tool bar, and/or the shank carrying implement when an obstruction is encountered in the soil.
Typically, shanks have also been mounted in such a manner that the shank (and in particular its actual ground engaging point) vibrate so as to reduce drag through the soil and also to produce better fracturing of the soil being cultivated. Therefore, the shank has usually been rigidly attached to the frame so as to inhibit the dampening of vibrations from the tractor and those generated by the tilling process.
Various structures have been used to attach shanks to a cultivating frame. One common configuration has been the use of a clamping member with an upper end clamped or bolted to the frame, where a shank member is secured in a yoke in the clamping member lower end by a suitable mounting pin or bolt and a suitable shear pin extending through two sets of aligned holes in the yoke and shank member. However, because of the inherent clearance between the bolt and the respective holes in the yoke and the shank member, this structure does not form a rigid attachment to the frame member, and therefore the vibrations transmitted to the ground working point of the shank are undesirably dampened. Further, the pins also require some form of restraint to prevent them from working out of position in use. Still further, since shear pins tend to bend and distort during the shearing process and when the shearing action is completed, the sheared portion of the shear pin is often difficult to remove from the holes in the yoke and the shank member. In order to reduce this difficulty in removing the distorted shear pin components, shear pins sometimes have had grooves machined into them at the point where shearing is desired to occur. However, such machining adds to the cost of the shear pin and, since the size of the radii of such grooves is critical to the force required to shear the pins (the smaller the radii the lower the shear force required), the unavoidable variation in the radii of such grooves reduces the predictability of the required clearing force (that is, such grooved shear pins have undesirably unpredictable failure).
Another common configuration has been to rigidly attach the shank directly to the frame of the implement or the tool bar by positioning the shank against the frame and then bolting a clamp member to the shank and about the frame, whereby the bolts will thereafter fail in tension should an obstruction be encountered. In one variation of that structure, the nuts attached to the bolts are of softer material so that, when an obstruction is encountered by the shank, it is the nut which fails (by stripping the internal thread of the nut) and thus the bolt is not damaged and may be reused. This configuration does generally tend to rigidly connect the frame and shank so as to transfer vibrations through to the ground working point as desired. However, refitting new bolts or nuts in a farm field after each failure occurs is often difficult and time consuming for a number of reasons. First, the soft nut material may smear into the threads of the reused bolt so that threading a new nut on the reused bolt can be difficult. Second, the torque to be applied to the nut during reinstallation of the shank member must be sufficient to adequately secure the shank member but not too great to cause stripping of the soft nut or failure of a soft bolt. Of course, obtaining this proper torque is particularly difficult if smeared metal remains on the reused bolt.
It is the object of the present invention to overcome and substantially ameliorate the above-described disadvantages and to enhance the usefulness of such systems in the field.